Is Legal Weed Really to Blame For a Rise in Emergency Room Visits?

According to federal law, cannabis is a dangerous substance. Legal cannabis opponents, all the way up to the United States Attorney General, Jeff Sessions, have cited an increase in cannabis-related emergency room visits to support this belief. But research about the relationship between increased cannabis access in states like Colorado and cannabis-related emergency room visits is more complicated than that.

Emergency room visits are reserved for cases like heart attacks, where patients require immediate care and are therefore not admitted prior to their treatment. Over the years, researchers have tried to find out whether increased access to cannabis results in an increase in emergency room visits. The results have been mixed.

One such study examined data from the Drug Abuse Warning Network to find out the number of emergency room visits for patients with cannabis in their systems between 2004 and 2011. Among patients older than 12 years old, the rate of emergency room visits for patients with just cannabis in their system increased from 51 to 73 visits per 100,000, and from 63 to 100 for those who had multiple drugs in their system.

But this data fails to answer one important question: were these emergency room visits a result of the cannabis in patients’ systems, or does this data simply reflect what we already know—that more people are using cannabis than before?

In Colorado, the first state to legalize recreational cannabis alongside Washington, a 2015 report from researchers at the Colorado Department of Public Health shows that cannabis-related hospitalizations are, in fact, increasing. But when we consider what constitutes a “cannabis-related hospitalization,” things start to get blurry.

In this report, researchers looked at the rate of hospitalizations among patients “with marijuana-related billing codes,” rather than visits that were a direct result of cannabis use. In other words, some of the patients counted in the data may have been hospitalized for reasons completely unrelated to cannabis and just happened to also use cannabis recently.

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As Politifact points out, emergency room visits are also much different than hospitalizations. Another study that compared emergency room visits by Colorado residents versus out-of-state visitors found that “ED visits related to cannabis use appear to be increasing more rapidly among out-of-state residents than among Colorado residents,” highlighting the importance of educating cannabis tourists on safe consumption practices. However, this study also relied on hospital codes that show whether a patient had used cannabis, but doesn’t specify its relevance to their emergency room visit. Therefore, the study was also only able to draw conclusions based on emergency room visits that were “possibly related to cannabis use.”

A third study from Colorado researchers points to yet anotherfactor in the state’s data on emergency room visits.

This study, published this year, concluded that “the prevalence of mental health conditions in ED visits with cannabis-associated diagnostic codes is higher than in those without cannabis.” But the researchers also specify that this could merely be coincidental, and a result of the increased use and availability of cannabis in the state.

Just this year, yet another Colorado study found that emergency room visits have increased in Colorado since recreational cannabis was officially legalized in 2014. But again, the data isn’t so clear-cut.

The researchers found that about two-thirds of the patients they studied also had diagnoses of depression and alcohol abuse, and that a significant number of these patients had consumed other substances, most commonly alcohol, before their emergency room visits. Other research has demonstrated that mixing alcohol and cannabis increases the THC levels in one’s bloodstream, which can dangerously accelerate one’s state of impairment.

As the first state to legalize recreational cannabis, it’s not surprising that much of this research has taken place in Colorado. But researchers from other states have also tried to determine the relationship between cannabis access and emergency room visits.

In 2014, researchers from Boston and Cleveland looked at 589 patients’ reported use of cannabis over the past three months and compared this to their “hospital utilization” and emergency room visits over the same timeframe. This time, the researchers concluded that “we were unable to detect an association between frequency of marijuana use and health, emergency department use, or hospital utilization.”

Two years later, researchers from Wisconsin conducted a similar study, using a larger sample size.

This study from 2016 examined 2011 to 2012 data from the National Health and Nutrition Examination Survey (NHANES), which interviewed over 174 million people, ages 18 to 59, about their cannabis use and trips to healthcare facilities like hospitals (12% of which didn’t respond).

Just like the study from Boston and Cleveland, these researchers found that cannabis use is not associated with “increased healthcare utilization,” meaning any visit to the doctor’s office or emergency room or “overnight hospital admission over the past year.” However, the survey data is only from 2011 to 2012, a short period of time before any state had legalized recreational cannabis and relies on self-reported data.

So does cannabis legalization cause emergency room visits to skyrocket? According to the data, maybe. But with so many factors involved including the reason for one’s emergency room visit, when a person consumed cannabis last, and whether they also consumed other substances, among other things—it’s difficult to make any definitive conclusions.

Clearly, more qualitative research is necessary. But what will prove most difficult for researchers is establishing whether cannabis is the direct cause of an increased number of emergency room visits or merely a factor.